1. Field of the Invention
The present invention relates to a unidirectional ratchet wrench, and more particularly to a unidirectional ratchet wrench that has excellent torsion-resisting force.
2. Description of Related Art
With reference to FIGS. 6 and 7, a conventional unidirectional ratchet wrench, invented by the applicant of this invention, is essentially composed of a wrench body (60) and a socket assembly.
The wrench body (60) has a toothed cavity (61) defined in one end of the wrench body (60) to receive the socket assembly in the toothed cavity (61). Multiple teeth (62) are formed longitudinally on an inner periphery of the toothed cavity (61). Each tooth (62) has an inclined face (621) and an upright face (623), and the inclined faces (621) of the teeth (62) are all arranged in the same direction.
The socket assembly is composed of a socket wheel (70), two pawls (74) and a split ring (76). A socket (71) is defined in the socket wheel (70) and is adapted to engage a nut or the similar fitting. Two pawl recesses (72) are defined longitudinally in an outer periphery of the socket wheel (70) to hold the two pawls (74) inside, and a groove (73) is defined around in the outer periphery of the socket wheel (70) to receive the split ring (76). Each pawl (74) is a curved sheet with a tapered thickness and a slot (741) transversally defined in the central part of an outer periphery of the pawl (74). A locking end (75) is formed on a thin edge of each pawl (74), and a lever end (751) formed on a thick edge opposite to the thin edge of each pawl (74). When the two pawls (74) are inside the pawl recesses (74) of the socket wheel (70), the slots (741) of the pawls align with the groove (73) in the socket wheel (70) and have a special cut or orientation to allow the pawls (74) to rock inside. The split ring (76) resiliently holds the pawls inside the pawl recesses (74) and compresses the lever end (53) of the pawls (74) to make the locking end (75) of the pawls lever outwardly. Whereby, the split ring (76) provides a restitution force on the pawls (74) to make the pawls (74) mate with the teeth (62) and then to lock the socket wheel (70) with the wrench body (60). Additionally, two locking rings (77) are mounted on opposite openings of the toothed cavity (61) to hold the socket assembly inside the wrench body (60).
When the conventional unidirectional ratchet wrench operates, the wrench body (60) is rotated to make the locking ends (751) of the pawls (74) engage the straight faces (623) of the teeth (62). Then, the socket wheel (70) is twisted by the wrench body (60) and rotates with the wrench body (60) so that a nut inside the socket (71) is also rotated. When the wrench body (60) is rotated in the opposite direction, the locking ends (751) of the pawls (74) move along the inclined faces (621) of the teeth (62). Then, the socket wheel (70) does not rotate with the wrench body, and the wrench is in an idle running state.
However, the conventional unidirectional ratchet wrench has the following drawbacks:
1. The slot (741) in each pawl (74) has to be defined precisely in a special cut and orientation. Otherwise, the pawl (74) cannot be levered to engage the locking end (75) with the teeth (61) perfectly, and then the torsion-resisting force of the conventional unidirectional ratchet wrench is weak.
2. The torsion-resisting efficiency of the wrench is provided by the locking ends (751) of the pawls (74) and is uneven and insufficient. Therefore, the split ring (74) easily deforms when the torsional force is slightly exceeded.
To make the unidirectional ratchet wrench endurable, the present invention has arisen to mitigate and/or obviate the disadvantage of the conventional unidirectional ratchet wrench.
The main objective of the present invention is to provide a unidirectional ratchet wrench that has excellent torsion-resisting efficiency.
Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.